The present invention relates to knee-joint endoprostheses of the kind consisting of a lower, tibia section to be anchored in the shin-bone by a shank, which section has, on either side of a central ridge which extends from front to rear, a bearing face which rises in a curve towards the front and which is hollowed out in cross-section, and of a femur section which is to be anchored in the thigh bone by a shank and which is provided with two pads which are yoked together across the ridge and are supported on the bearing faces.
Known knee-joint endoprostheses of the kind described above have to be screwed together when the operation is performed to fit them and in them, when the knee is bent, the pads of the femur section slide on either side of a central ridge on the tibia section in curved hollowed-out bearing faces of constant width and are forcibly guided by a transverse pin associated with the femur section which passes through a curved slot in the central ridge as set forth in German Offenlegungsschrift No. 2,244,064. As result it is not possible to simulate the natural action of and the physiological conditions prevailing in a healthy knee-joint.
An object of the invention is to make it possible, when the joint is in bent positions, for the femur section to perform a limited, self-adjusting forward movement in relation to the tibia section to suit the attachment of the tendons of the leg and for the prosthesis to permit the lower leg a limited rotary movement relative to the thigh, and also for any screwed assembly of the two parts of the joint to be avoided when an operation is performed to fit the prosthesis.